There is a need for solvent-free, low viscosity hot melt adhesive (HMA) and pressure sensitive adhesive (PSA) formulations that maintain adhesive strength at high use temperatures (for example, 104° F. (40° C.) and above).
There is also a need for solvent-free, low viscosity adhesive formulations that can be used in a variety of applications, including, but not limited to, case and carton sealing, automotive, graphic arts, nonwovens, panel assembly, high performance tapes, contact hot melt adhesives, paperboard coatings, inks, personal care and cosmetic products, sealants, color and additive concentrates, carpet-tape adhesives, and woodworking adhesives.
Currently, some of the high performance pressure sensitive adhesives (PSA) based on high molecular weight (W) styrene block copolymers (SBCs) can only be produced using solvents. They can not be applied from a hot melt, due to their high viscosity (molecular weight). The trend is to use solvent-free adhesives for both environmental and cost reasons. Also, reactive hot melts based on urethane chemistry are expensive and have safety issues, since they utilize isocyanate chemistry.
U.S. Publication No. 2005/0043455 discloses crystalline polyolefin homopolymer or copolymer waxes, modified free-radically with a silane compound, and having a viscosity, as measured at 170° C., of between 10 and 50,000 mPa·s, and a heat of fusion >10 J/g. The silane compound used for modification includes at least one olefinic double bond and at least one alkoxy radical attached directly to silicon. The polyolefin waxes used for modification are prepared using a metallocene catalyst (see abstract). This reference discloses the use of high levels of free radical initiator, 0.1 to 10 percent by weight, based on the polyolefin wax, relative to the amount of silane employed, 0.1 to 40 percent by weight, based on the polyolefin wax, (for example, see paragraphs [0097], [0098] and [0116]). European Patent EP 0 944 670 B1 discloses a crosslinkable elastomer composition that includes a silane grafted ethylene alpha-olefin interpolymer elastomer with a hardness (Shore A)≦85, and, optionally, a crystalline olefin polymer. Exposure to moisture converts the crosslinkable composition into a nonporous, grafted and crosslinked elastomer composition that has a hardness (Shore A)≦85 and an abrasion resistance that is greater than that of the crosslinkable composition (see abstract). This patent discloses the use of a preferred amount of silane, 0.1 to 3.5 weight percent, and relatively high levels of initiator, with a ratio of silane to initiator from 10:1 to 30:1 (for example, see paragraphs [0026] and [0027]).
International Publication No. WO 2005/100501 discloses an article comprising 1) a functionalized component, 2) tackifier, and 3) an olefin polymer, comprising one or more C3 to C40 olefins, optionally one or more diolefins, and less than 5 mole of ethylene, and having a Dot T-Peel of one Newton or more, a branching index (g′) of 0.95 or less, measured at the Mz of the polymer; and an Mw of 100,000 or less. The functional component is selected from the group consisting of functionalized polymers, functionalized oligomers and beta nucleating agents (see abstract). The experimental examples in this reference are mainly directed to maleic anhydride grafted polypropylene base polymers.
U.S. Pat. No. 5,824,718 discloses curable, silane-grafted substantially linear ethylene polymers, which are useful as wire and cable coatings, weatherstripping, fibers. These silane-grafted polymers can be either filled or unfilled, and cure quickly relative to many commercial coatings (see abstract). This patent discloses ethylene/α-olefin base polymers with a preferred melt index (12) from 0.5 to 200 g/10 min (for example, see column 4, lines 7-10). See also related patents, U.S. Pat. No. 5,741,858 and U.S. Pat. No. 6,048,935. U.S. Pat. No. 4,806,594 discloses a water curable composition comprising: (a) at least one polymer selected from the group consisting of silane grafted homopolymers of ethylene, propylene, or 1-butene (see abstract). In the examples of this patent, a relatively high molecular weight polyethylene is silanated (see Examples 1-19).
U.S. Pat. No. 5,995,474 discloses an adhesive composition which comprises a silane-grafted, largely amorphous poly-α-olefin, prepared by grafting onto this amorphous poly-α-olefin a silane compound having from 1-3 alkoxy groups, attached directly to the silicon, and at least one olefinic double bond containing moiety, and then crosslinking the adhesive composition by means of water (see abstract). This patent is mainly directed to propylene base polymers. Additional grafted polymers are disclosed in U.S. Pat. No. 5,994,474; U.S. Pat. No. 5,705,565; U.S. Pat. No. 6,414,102; U.S. Pat. No. 6,043,401; U.S. Pat. No. 5,498,809; U.S. Pat. No. 5,266,627; and EP 0850138B1. Grafted blend compositions are disclosed in U.S. Pat. Nos. 6,395,791; 6,583,222; 6,583,188. The following patents/applications are primarily directed to base polymers: U.S. Pat. No. 6,172,015; U.S. Pat. No. 6,335,410; U.S. Pat. No. 4,039,560; U.S. 2003114322 (WO 01/072855); WO 03/087178; WO 03/040201; WO 90/01503; WO 04/031292; and WO 04/035680.
There is a need for silanated polyolefins with excellent adhesion properties for use in adhesive compositions. There is a further need for solvent-free adhesives for both environmental and cost reasons. These issues have been satisfied by the silanated polyolefins of the invention, and adhesive formulations based on these polyolefins. The silanated polymers used in the adhesive formulations have similar performance to the SBC-based, high performance tapes, without the need for a solvent. In addition, the silanated polyolefin polymers described herein are cheaper and safer to use. Moreover, the moisture curable silane chemistry allows one to use hot melt adhesives, such as in automotive, under the hood applications, which require high temperature performance capabilities (104° F. (40° C.) or above). The silanated polyolefins of the invention can be used to prepare adhesive formulations for both hot melt and pressure sensitive applications.